INTRODUCTION
SOME CLAIM THAT JAVASCRIPT is now the most popular programming language in the world, running any number of complex web applications that the world relies on to do business, make purchases, manage processes, and more.
JavaScript is very loosely based on Java, an object-oriented programming language popularized for use on the Web by way of embedded applets. Although JavaScript has a similar syntax and programming methodology, it is not a “light” version of Java. Instead, JavaScript is its own dynamic language, finding its home in web browsers around the world and enabling enhanced user interaction on web sites and web applications alike.
In this book, JavaScript is covered from its very beginning in the earliest Netscape browsers to the present-day incarnations flush with support for the DOM and Ajax. You learn how to extend the language to suit specific needs and how to create seamless client-server communication without intermediaries such as Java or hidden frames. In short, you learn how to apply JavaScript solutions to business problems faced by web developers everywhere.
WHO THIS BOOK IS FOR
This book is aimed at three groups of readers:
- Experienced developers familiar with object-oriented programming who are looking to learn JavaScript as it relates to traditional OO languages such as Java and C++.
- Web application developers attempting to enhance the usability of their web sites and web applications.
- Novice JavaScript developers aiming to better understand the language.
In addition, familiarity with the following related technologies is a strong indicator that this book is for you:
- Java
- PHP
- ASP.NET
- HTML
- CSS
- XML
This book is not aimed at beginners lacking a basic computer science background or those looking to add some simple user interactions to web sites. These readers should instead refer to Wrox’s Beginning JavaScript, 4th Edition (Wiley, 2009).
WHAT THIS BOOK COVERS
Professional JavaScript for Web Developers, 3rd Edition, provides a developer-level introduction, along with the more advanced and useful features of JavaScript.
Starting at the beginning, the book explores how JavaScript originated and evolved into what it is today. A detailed discussion of the components that make up a JavaScript implementation follows, with specific focus on standards such as ECMAScript and the Document Object Model (DOM). The differences in JavaScript implementations used in different popular web browsers are also discussed.
Building on that base, the book moves on to cover basic concepts of JavaScript including its version of object-oriented programming, inheritance, and its use in HTML. An in-depth examination of events and event handling is followed by an exploration of browser detection techniques. The book then explores new APIs such as HTML5, the Selectors API, and the File API.
The last part of the book is focused on advanced topics including performance/memory optimization, best practices, and a look at where JavaScript is going in the future.
HOW THIS BOOK IS STRUCTURED
This book comprises the following chapters:
1. What Is JavaScript? — Explains the origins of JavaScript: where it came from, how it evolved, and what it is today. Concepts introduced include the relationship between JavaScript and ECMAScript, the Document Object Model (DOM), and the Browser Object Model (BOM). A discussion of the relevant standards from the European Computer Manufacturer’s Association (ECMA) and the World Wide Web Consortium (W3C) is also included.
2. JavaScript in HTML — Examines how JavaScript is used in conjunction with HTML to create dynamic web pages. Introduces the various ways of embedding JavaScript into a page including a discussion surrounding the JavaScript content-type and its relationship to the <script> element.
3. Language Basics — Introduces basic language concepts including syntax and flow control statements. Explains the syntactic similarities of JavaScript and other C-based languages and points out the differences. Type coercion is introduced as it relates to built-in operators.
4. Variables, Scope, and Memory — Explores how variables are handled in JavaScript given their loosely typed nature. A discussion about the differences between primitive and reference values is included, as is information about execution context as it relates to variables. Also, a discussion about garbage collection in JavaScript explains how memory is reclaimed when variables go out of scope.
5. Reference Types — Covers all of the details regarding JavaScript’s built-in reference types, such as Object and Array. Each reference type described in ECMA-262 is discussed both in theory and in how they relate to browser implementations.
6. Object-Oriented Programming — Explains how to use object-oriented programming in JavaScript. Since JavaScript has no concept of classes, several popular techniques are explored for object creation and inheritance. Also covered in this chapter is the concept of function prototypes and how that relates to an overall OO approach.
7. Function Expressions — Explores one of the most powerful aspects of JavaScript: function expressions. Topics include closures, how the this object works, the module pattern, and creating private object members.
8. The Browser Object Model — Introduces the Browser Object Model (BOM), which is responsible for objects allowing interaction with the browser itself. Each of the BOM objects is covered, including window, document, location, navigator, and screen.
9. Client Detection — Explains various approaches to detecting the client machine and its capabilities. Different techniques include capability detection and user-agent string detection. Each approach is discussed for pros and cons, as well as situational appropriateness.
10. The Document Object Model — Introduces the Document Object Model (DOM) objects available in JavaScript as defined in DOM Level 1. A brief introduction to XML and its relationship to the DOM gives way to an in-depth exploration of the entire DOM and how it allows developers to manipulate a page.
11. DOM Extensions — Explains how other APIs, as well as the browsers themselves, extend the DOM with more functionality. Topics include the Selectors API, the Element Traversal API, and HTML5 extensions.
12. DOM Levels 2 and 3 — Builds on the previous two chapters, explaining how DOM Levels 2 and 3 augmented the DOM with additional properties, methods, and objects. Compatibility issues between Internet Explorer and other browsers are discussed.
13. Events — Explains the nature of events in JavaScript, where they originated, legacy support, and how the DOM redefined how events should work. A variety of devices are covered including the Wii and iPhone.
14. Scripting Forms — Looks at using JavaScript to enhance form interactions and work around browser limitations. Discussion focuses on individual form elements such as text boxes and select boxes and on data validation and manipulation.
15. Graphics with Canvas — Discusses the <canvas> tag and how to use it to create on-the-fly graphics. Both the 2D context and the WebGL (3D) context are covered, giving you a good starting point for creating animations and games.
16. HTML5 Scripting — Introduces JavaScript API changes as defined in HTML5. Topics include cross-document messaging, the Drag-and-Drop API scripting <audio> and <video> elements, as well as history state management.
17. Error Handling and Debugging — Discusses how browsers handle errors in JavaScript code and presents several ways to handle errors. Debugging tools and techniques are also discussed for each browser, including recommendations for simplifying the debugging process.
18. XML in JavaScript — Presents the features of JavaScript used to read and manipulate eXtensible Markup Language (XML) data. Explains the differences in support and objects in various web browsers and offers suggestions for easier cross-browser coding. This chapter also covers the use of eXtensible Stylesheet Language Transformations (XSLT) to transform XML data on the client.
19. ECMAScript for XML — Discusses the ECMAScript for XML (E4X) extension to JavaScript, which is designed to simplify working with XML. Explains the advantages of E4X over using the DOM for XML manipulation.
20. JSON — Introduces the JSON data format as an alternative to XML. Browser-native JSON parsing and serialization are discussed as are security considerations when using JSON.
21. Ajax and Comet — Looks at common Ajax techniques including the use of the XMLHttpRequest object and Cross-Origin Resource Sharing (CORS) for cross-domain Ajax. Explains the differences in browser implementations and support and provides recommendations for usage.
22. Advanced Techniques — Dives into some of the more complex JavaScript patterns, including function currying, partial function application, and dynamic functions. Also covers creating a custom event framework to enable simple event support for custom objects and creating tamper-proof objects using ECMAScript 5.
23. Offline Applications and Client-Side Storage — Discusses how to detect when an application is offline and provides various techniques for storing data on the client machine. Begins with a discussion of the most commonly supported feature, cookies, and then discusses newer functionality such as Web Storage and IndexedDB.
24. Best Practices — Explores approaches to working with JavaScript in an enterprise environment. Techniques for better maintainability are discussed, including coding techniques, formatting, and general programming practices. Execution performance is discussed, and several techniques for speed optimization are introduced. Last, deployment issues are discussed, including how to create a build process.
25. Emerging APIs — Introduces APIs being created to augment JavaScript in the browser. Even though these APIs aren’t yet complete or fully implemented, they are on the horizon, and browsers have already begun partially implementing their features. Includes discussion of Web Timing, geolocation, and the File API.
WHAT YOU NEED TO USE THIS BOOK
To run the samples in the book, you need the following:
- Windows XP, Windows 7, or Mac OS X
- Internet Explorer 6 or higher, Firefox 2 or higher, Opera 9 or higher, Chrome, or Safari 2 or higher
The complete source code for the samples is available for download from the web site at www.wrox.com.
CONVENTIONS
To help you get the most from the text and keep track of what’s happening, we’ve used a number of conventions throughout the book.
Boxes with a warning icon like this one hold important, not-to-be forgotten information that is directly relevant to the surrounding text.
The pencil icon indicates notes, tips, hints, tricks, and asides to the current discussion.
As for styles in the text:
- We highlight new terms and important words when we introduce them.
- We show keyboard strokes like this: Ctrl+A.
- We show file names, URLs, and code within the text like so: persistence.properties.
- We present code in two different ways:
We use a monofont type with no highlighting for most code examples.
We use bold to emphasize code that's particularly important in the present context.
SOURCE CODE
As you work through the examples in this book, you may choose either to type in all the code manually or to use the source code files that accompany the book. All the source code used in this book is available for download at www.wrox.com. When at the site, simply locate the book’s title (use the Search box or one of the title lists) and click the Download Code link on the book’s detail page to obtain all the source code for the book. Code that is included on the web site is highlighted by the following icon:
Listings include the file name in the title. If it is just a code snippet, you’ll find the file name in a code note such as this:
Code snippet file name
Because many books have similar titles, you may find it easiest to search by ISBN; this book’s ISBN is 978-1-118-02669-4.
Once you download the code, just decompress it with your favorite compression tool. Alternately, you can go to the main Wrox code download page at www.wrox.com/dynamic/books/download.aspx to see the code available for this book and all other Wrox books.
ERRATA
We make every effort to ensure that there are no errors in the text or in the code. However, no one is perfect, and mistakes do occur. If you find an error in one of our books, like a spelling mistake or faulty piece of code, we would be very grateful for your feedback. By sending in errata you may save another reader hours of frustration and at the same time you will be helping us provide even higher quality information.
To find the errata page for this book, go to www.wrox.com and locate the title using the Search box or one of the title lists. Then, on the book details page, click the Book Errata link. On this page you can view all errata that have been submitted for this book and posted by Wrox editors. A complete book list including links to each book’s errata is also available at www.wrox.com/misc-pages/booklist.shtml.
If you don’t spot “your” error on the Book Errata page, go to www.wrox.com/contact/techsupport.shtml and complete the form there to send us the error you have found. We’ll check the information and, if appropriate, post a message to the book’s errata page and fix the problem in subsequent editions of the book.
P2P.WROX.COM
For author and peer discussion, join the P2P forums at p2p.wrox.com. The forums are a Web-based system for you to post messages relating to Wrox books and related technologies and interact with other readers and technology users. The forums offer a subscription feature to e-mail you topics of interest of your choosing when new posts are made to the forums. Wrox authors, editors, other industry experts, and your fellow readers are present on these forums.
At p2p.wrox.com you will find a number of different forums that will help you not only as you read this book but also as you develop your own applications. To join the forums, just follow these steps:
1. Go to p2p.wrox.com and click the Register link.
2. Read the terms of use and click Agree.
3. Complete the required information to join, as well as any optional information you wish to provide, and click Submit.
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You can read messages in the forums without joining P2P, but in order to post your own messages, you must join.
Once you join, you can post new messages and respond to messages other users post. You can read messages at any time on the Web. If you would like to have new messages from a particular forum e-mailed to you, click the Subscribe to this Forum icon by the forum name in the forum listing.
For more information about how to use the Wrox P2P, be sure to read the P2P FAQs for answers to questions about how the forum software works, as well as many common questions specific to P2P and Wrox books. To read the FAQs, click the FAQ link on any P2P page.